1. Filed of the Invention
This invention relates to systems and methods for driving an electrostatically actuated device using an electronic drive signal.
2. Description of the Related Art
One type of electrostatically actuated device with which the systems and methods of this invention may be used is micromachined fluid ejectors. Fluid ejectors have been developed for ink jet recording or printing, as well as other uses. Ink jet recording apparatus offer numerous benefits, including extremely quiet operation when recording, high speed printing, a high degree of freedom in ink selection, and the ability to use low-cost plain paper. The so-called xe2x80x9cdrop-on-demandxe2x80x9d drive method, where ink is output only when required for recording, is now the conventional approach. The drop-on-demand drive method makes it unnecessary to recover ink not needed for recording.
Fluid ejectors, including those used for ink jet printing, include one or more nozzles that allow the formation and control of small ink droplets to permit high resolution, resulting in the ability to print sharper characters with improved tonal resolution. In particular, drop-on-demand ink jet print heads are generally used for high resolution printers.
Drop-on-demand technology generally uses some type of pulse generator to form and eject drops. For example, in one type of print head, a chamber having an ink nozzle may be fitted with a piezoelectric wall that is deformed when a voltage is applied. As a result of the deformation, the fluid is forced out of the nozzle orifice as a drop. The drop then impinges directly on an associated printing surface. Use of such a piezoelectric device as a driver is described in JP B-1990-51734.
Another type of print head uses bubbles formed by heat pulses to force fluid out of the nozzle. The drops are separated from the ink supply when the bubbles form. Use of pressure generated by heating the ink to generate bubbles is described in JP B-1986-59911.
Yet another type of drop-on-demand print head incorporates an electrostatic actuator. This type of print head utilizes electrostatic force to eject the ink. Examples of such electrostatic print heads are disclosed in U.S. Pat. No. 4,520,375 to Kroll and Japanese Laid-Open Patent Publication No. 289351/90. The ink jet head disclosed in the 375 patent uses an electrostatic actuator comprising a diaphragm that constitutes a part of an ink ejection chamber and a base plate disposed outside of the ink ejection chamber opposite to the diaphragm. The ink jet head ejects ink droplets, through a nozzle communicating with the ink ejection chamber, by applying a time-varying voltage between the diaphragm and the base plate. The diaphragm and the base plate thus act as a capacitor, which causes the diaphragm to be set into mechanical motion and the fluid to exit responsive to the diaphragm""s motion.
On the other hand, the ink jet head discussed in the Japan 351 distorts its diaphragm by applying a voltage to an electrostatic actuator fixed on the diaphragm. This result in suction of ink into an ink ejection chamber. Once the voltage is removed, the diaphragm is restored to its non-distorted condition, ejecting ink from the ink over-filled ejection chamber.
Fluid drop ejectors may be used not only for printing, but also for depositing photoresist and other liquids in the semiconductor and flat panel display industries, for delivering drug and biological samples, for delivering multiple chemicals for chemical reactions, for handling DNA sequences, for delivering drugs and biological materials for interaction studies and assaying, and for depositing thin and narrow layers of plastics for usable as permanent and/or removable gaskets in micro-machines.
This invention provides systems and methods that allow efficient actuation of electrostatically driven devices.
This invention separately provides systems and methods for electrostatic actuation using a constant electric field force.
This invention separately provides systems and methods that generate increased ejection force for electrostatically actuated fluid ejectors.
This invention separately provides systems and methods for electrostatic actuation in which potential electrochemical reactions are reduced.
This invention separately provides systems and methods for electrostatic actuation in which conductivity losses are reduced.
This invention separately provides systems and methods for electrostatic actuation in which the potential for dielectric breakdown is reduced.
This invention separately provides systems and methods for xe2x80x9con demandxe2x80x9d drop size modulation for electrostatically actuated fluid ejectors.
In various exemplary embodiments of the systems and methods according to this invention, a drive signal is applied to an electrostatically actuated device, such that a resulting electric field has a constant force. In various exemplary embodiments, the drive signal may applied by a constant current source. Alternatively, in various other exemplary embodiments, the drive signal may be reduced over the course of its lifetime.
In various exemplary embodiments of the systems and methods according to this invention, an electrostatically actuated device is driven at a rate that reduces the potential effects of electrochemical reactions.
In various exemplary embodiments of the systems and methods according to this invention, a bi-polar drive signal is applied to an electrostatically actuated device such that the potential effects of electrochemical reactions are reduced.
In various exemplary embodiments of the systems and methods according to this invention, a drive signal of a suitably high frequency is applied to an electrostatically actuated device such that the potential of electrochemical reactions or electrical breakdown, or both, is reduced.